Breakaway deployment cable for underwater seismic recording system

Abstract

A seismic cable system for joining the free ends of a seismic cable utilizing a connector which will separate when subject to a predetermined load. The system includes a first cable connector section that is rotatingly mounted directly on a first free cable end and a second cable connector section that is rotatingly mounted directly on a second free cable end. One cable connector section seats within the other cable connector section and the two sections are fixed to one another with a shear pin. The system is particularly useful when utilizing non-conducting, flexible cable or rope to deploy and retrieve a plurality of stand-alone, self-contained seismic data acquisition units secured to the cable.

1. A marine seismic recording system comprising:
 a first length of cable having opposite ends; 
 a second length of cable having opposite ends; 
 a shear connector attaching said first and second lengths of cable, said shear connector comprising
 a first fitting directly attached to an end of the first length of cable; 
 a second fitting directly attached to an end of the second length of cable, said first fitting seated in the second fitting; 
 a shear pin inserted through said fittings thereby securing said fittings together, and at least one seismic recording device attached to one of said lengths of cable. 
 
 
   
   
     2. The marine seismic recording system of  claim 1  wherein each fitting has a bore extending from a first end of the fitting to a second end of the fitting and wherein each fitting has an aperture passing through opposing sides of each fitting. 
   
   
     3. The marine seismic recording system of  claim 2  wherein the first fitting is at least partially seated inside the second fitting such that the apertures in the respective first and second fittings are aligned. 
   
   
     4. The marine seismic recording system of  claim 3  wherein said shear pin passes through the aligned apertures to join the first and second fitting to one another. 
   
   
     5. The marine seismic recording system of  claim 1  wherein each fitting has a bore extending from a first end of the fitting to a second end of the fitting. 
   
   
     6. The marine seismic recording system of  claim 5  wherein each fitting has a shoulder defined in the bore at the first end and the end of the respective lengths of cable pass through their respective bore. 
   
   
     7. The marine seismic recording system of  claim 6  wherein each end of cable passing through the bore at the first end of the fitting has a stop attached to said cable such that said stop on said cable abuts said shoulder of said fitting, thereby securing said fitting on said cable. 
   
   
     8. The marine seismic recording system of  claim 7  wherein the shoulder is formed by a restriction in the bore. 
   
   
     9. The marine seismic recording system of  claim 8  wherein the bore is characterized by an internal diameter and the restriction is formed by a taper in the bore diameter. 
   
   
     10. The marine seismic recording system of  claim 1  wherein each fitting has a first end and a second end and each fitting is characterized by an inner diameter and an outer diameter and wherein the outer diameter of the first fitting at the second end of the first fitting is smaller than the inner diameter of the second fitting at the second end of the second fitting and the second end of the first fitting is engaged by the second end of the second fitting. 
   
   
     11. The marine seismic recording system of  claim 1  wherein each fitting has a first end and a second end and the first fitting has a protrusion at its second end and the second fitting has a opening at its second end and wherein the protrusion of the first fitting seats in the opening of the second fitting. 
   
   
     12. The marine seismic recording system of  claim 1  wherein said cable is a non-rigid cable. 
   
   
     13. The marine seismic recording system of  claim 1  wherein said cable is non-conducting. 
   
   
     14. The marine seismic recording system of  claim 1  wherein said cable has a negative buoyancy less than said multiple seismic data collection units attached thereto. 
   
   
     15. The marine seismic recording system of  claim 1  wherein said cable is rope. 
   
   
     16. A marine seismic recording system comprising:
 a first length of cable having opposite ends; 
 a second length of cable having opposite ends; 
 a shear connector attaching said first and second lengths of cable, said shear connector comprising
 a first fitting directly attached to an end of the first length of cable; 
 a second fitting directly attached to an end of the second length of cable, said first fitting seated in the second fitting; 
 a shear pin inserted through said fittings thereby securing said fittings together, and, at least one seismic recording device attached to one of said lengths of cable, 
 wherein each of said first and second fittings are rotatingly mounted on said respective cable ends. 
 
 
   
   
     17. A marine seismic recording system utilizing a break-away cable connector, said system comprising:
 a plurality of non-conducting cable segments, wherein each cable segment has a first end and a second end; 
 a plurality of marine seismic recording devices wherein a marine seismic recording device is attached to at least one of the cable segments; 
 a plurality of first fittings, each having a first end and a second open end, each of said first fittings attached to the first end of a cable segment; 
 a plurality of second fittings, each having a first end and a second end, each of said second fittings attached to the second end of a cable segment and wherein said second end of said second fitting nests inside of said second open end of an adjacent first fitting; and 
 a shear pin securing each of said nested first and second fittings to one another. 
 
   
   
     18. The system of  claim 17  further comprising a stop adjacent each of said first ends of the fittings for securing each of said first ends on the corresponding cable end. 
   
   
     19. The system of  claim 17  wherein an aperture is defined between said first and second ends of at least one of said fittings, said aperture being defined by a first portion adjacent said first end and a second portion adjacent said second end. 
   
   
     20. The system of  claim 19  wherein said second portion of said aperture has a substantially similar inner diameter along its length and said first portion of said aperture has an inner diameter that tapers along its length. 
   
   
     21. The system of  claim 20  wherein a shoulder is defined in the first portion of said aperture. 
   
   
     22. The system of  claim 21 , wherein said stop abuts said shoulder.